U.S. patent application number 11/576985 was filed with the patent office on 2008-12-04 for circuit working with acoustic volume waves and component connected to the circuit.
This patent application is currently assigned to EPCOS AG. Invention is credited to Veit Meister, Werner Ruile.
Application Number | 20080297277 11/576985 |
Document ID | / |
Family ID | 35500860 |
Filed Date | 2008-12-04 |
United States Patent
Application |
20080297277 |
Kind Code |
A1 |
Meister; Veit ; et
al. |
December 4, 2008 |
Circuit Working With Acoustic Volume Waves And Component Connected
To The Circuit
Abstract
A circuit for use with bulk acoustic waves includes a first
electroacoustic system in a first branch and a second
electroacoustic system in a second branch. The first
electroacoustic system includes a first resonator and a second
resonator that are in series in the first branch, and that are
galvanically separated, and acoustically coupled, by a first
coupling system. The second electroacoustic system includes a first
resonator and a second resonator that are connected in series in
the second branch, and that are galvanically separated, and
acoustically coupled, by a second coupling system. The first and
second electroacoustic systems are acoustically coupled via the
first and second coupling systems and/or electrically coupled.
Inventors: |
Meister; Veit; (Kagel,
DE) ; Ruile; Werner; (Munich, DE) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
EPCOS AG
Munich
DE
|
Family ID: |
35500860 |
Appl. No.: |
11/576985 |
Filed: |
September 23, 2005 |
PCT Filed: |
September 23, 2005 |
PCT NO: |
PCT/EP2005/010336 |
371 Date: |
July 15, 2008 |
Current U.S.
Class: |
333/189 ;
333/133 |
Current CPC
Class: |
H03H 9/0095 20130101;
H03H 9/584 20130101; H03H 9/02228 20130101 |
Class at
Publication: |
333/189 ;
333/133 |
International
Class: |
H03H 9/205 20060101
H03H009/205 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 11, 2004 |
DE |
10 2004 049 499.1 |
Claims
1. A circuit for use with bulk acoustic waves, the circuit
comprising: a first electroacoustic system in a first branch; and a
second electroacoustic system in a second branch; wherein the first
electroacoustic system comprises a first resonator and a second
resonator that are in series in the first branch, and that are
galvanically separated, and acoustically coupled by a first
coupling system; wherein the second electroacoustic system
comprises a first resonator and a second resonator that are
connected in series in the second branch, and that are galvanically
separated, and acoustically coupled by a second coupling system;
wherein the first and second electroacoustic systems are
acoustically coupled via the first and second coupling systems
and/or are electrically coupled.
2. The circuit of claim 2, wherein the first and second
electroacoustic systems are electrically coupled.
3. The circuit according to claim 1, further comprising: a first
electric port and a second electric port, wherein at least one of
the first and second electric ports is symmetrically
interconnected; wherein a first signal path is between first
terminals of the first and second electric ports; wherein a second
signal path is between second terminals of the first and second
electric ports; and wherein the first branch corresponds to the
first signal path and the second branch corresponds to the second
signal path.
4. The circuit of claim 1, further comprising: a first electric
port and a second electric port, wherein at least one of the first
and second electric ports is symmetrically interconnected; wherein
a first signal path is between first terminals of the first and
second electric ports; wherein a second signal path is between
second terminals of the first and second electric ports, and
wherein the first branch comprises a first shunt arm connecting the
first and second signal paths, and the second branch comprises a
second shunt arm in parallel with the first shunt arm.
5. The circuit of claim 1, wherein the first and second coupling
systems are electrically connected via a floating electrical
connection.
6. The circuit of claim 1, wherein the first and second coupling
systems are capacitively or inductively coupled.
7. The circuit of claim 1, wherein the first and second coupling
systems are connected electrically via an electrical connection
connected to a first reference potential.
8. The circuit of claim 1, wherein the first resonators of the
first and second electroacoustic systems are connected electrically
in series.
9. The circuit of claim 1, wherein the second resonators of the
first and second electroacoustic systems are connected electrically
in series.
10. The circuit of claim 1, wherein the first resonators of the
first and second electroacoustic systems are connected electrically
in parallel.
11. The circuit of claim 1, wherein the second resonators of the
first and second electroacoustic systems are connected electrically
in parallel.
12. The circuit of claim 3, wherein the second terminal of the
first electric port is electrically connected to a first reference
potential.
13. The circuit of claim 1, wherein the first resonator, the first
coupling system, and the second resonator of the first
electroacoustic system are arranged in a first resonator stack;
wherein the first resonator, the second coupling system, and the
second resonator of the second electroacoustic system are arranged
in a second resonator stack.
14. The circuit of claim 13, wherein the first and second resonator
stacks are electrically connected.
15. The circuit of claim 1, wherein the first coupling system
comprises a first sub-structure and a second sub-structure; wherein
the first resonator of the first electroacoustic system and the
first sub-structure of the first coupling system form a first
resonator stack; wherein the second resonator of the first
electroacoustic system and the second sub-structure of the first
coupling system form a second resonator stack; and wherein the
first and second substructures of the first coupling system are
electrically connected via an additional electrical connection.
16. The circuit of claim 15, wherein the second coupling system
comprises a first sub-structure and a second sub-structure; wherein
the first resonator of the second electroacoustic system and the
first sub-structure of the second coupling system form a third
resonator stack; wherein the second resonator of the second
electroacoustic system and the second sub-structure of the second
coupling system form a fourth resonator stack; and wherein the
first and second substructures of the second coupling system are
electrically connected via an additional electrical connection.
17. The circuit of claim 15, wherein the first and second
sub-structures of the first coupling system are capacitively or
inductively coupled.
18. The circuit of claim 12, wherein the second resonator of the
first electroacoustic system is between the first terminal of the
second electric port and a second reference potential; and wherein
the second resonator of the second electroacoustic system is
between the second terminal of the second electric port and a third
reference potential.
19. The circuit of claim 1, further comprising: one or more
additional electroacoustic systems, each additional electroacoustic
system being in a corresponding branch; wherein each additional
electroacoustic system comprises series-connected resonators that
are galvanically separated, and acoustically coupled via a coupling
system; and wherein the electroacoustic systems are acoustically
coupled via coupling systems and/or are electrically coupled.
20. The circuit of claim 3, wherein an impedance of the first
electric port differs from an impedance of the second electric port
by a factor of two or more.
21. The circuit of claim 1, further comprising: a first electric
port and a second electric port, wherein at least one of the first
and second electric ports is symmetrically interconnected; a first
signal path between first terminals of the first and second
electric ports; a second signal path between second terminals of
the first and second electric ports; wherein the first branch
corresponds to the first signal path; and wherein the second branch
corresponds to a first shunt arm connecting the first and second
signal paths.
22. A component comprising: the circuit of claim 1; wherein
resonators of the electroacoustic systems operate with guided bulk
acoustic waves; wherein each resonator comprises a transducer and a
piezoelectric layer arranged therebelow or thereabove; and wherein
each piezoelectric layer corresponds to a coupling system.
23. The component of claim 22, wherein resonators of a same
electroacoustic system that are acoustically coupled are arranged
in a stack and are acoustically coupled vertically.
24. The component of claim 22, wherein resonators of a same
electroacoustic system that are acoustically coupled are arranged
side-by-side in a longitudinal direction and are acoustically
coupled in the longitudinal direction
25. The component of claim 22, wherein resonators of a same
electroacoustic system that are acoustically coupled are arranged
side-by-side in a transverse direction and are acoustically coupled
in the transverse direction
Description
[0001] The invention relates to a circuit operating with bulk
acoustic waves, in particular, a bandpass filter.
[0002] Filters operating with bulk acoustic waves--stacked crystal
filters--with thin-film resonators (FBAR=Thin Film Bulk Acoustic
Resonator) stacked one atop the other are known from the
publication U.S. Pat. No. 5,910,756. A circuit comprising two
symmetric electrical ports is known from FIG. 12 of that
publication.
[0003] The problem of the invention is to create an additional
circuit operating with acoustic waves that is suitable for a
symmetric/symmetric or an asymmetric/symmetric operation, as well
as realizing other functionalities.
[0004] The problem of the invention is solved by a circuit
according to claim 1. Advantageous configurations and refinements
of the invention follow from the additional claims.
[0005] The invention relates to a circuit operating with bulk
acoustic waves, with at least two electroacoustic systems, each
arranged in a branch. Each electroacoustic system comprises at
least two resonators connected in series in the respective branch,
which are galvanically separated from one another and acoustically
coupled to one another by means of a coupling system arranged
between them.
[0006] Here, two different electroacoustic systems are arranged in
branches different from one another. The electroacoustic systems
are electroacoustically coupled to one another via their coupling
systems. An electroacoustic coupling is understood to mean an
acoustic and/or electrical coupling.
[0007] The electroacoustic coupling between two electroacoustic
systems by means of their coupling systems is referred to below
simply as coupling.
[0008] A resonator operating with bulk waves--preferably a
thin-film resonator or FBAR (Thin Film Bulk Acoustic Wave
Resonator)--comprises a piezoelectric layer arranged between two
electrodes. Each resonator is characterized by its resonance
frequency and its antiresonance frequency. Resonators can each
contribute to the appearance of poles in the transfer function. Two
coupled resonators generate an additional pole.
[0009] The coupling between different branches of a circuit can
therefore be exploited to produce additional poles, whereby, for
example, the suppression in a stopband of the circuit can be
increased.
[0010] By galvanically decoupling the resonators arranged on the
input side and the output side, the circuit can be successfully
operated in balanced/balanced mode or in unbalanced/balanced mode.
In one variant, a difference-forming circuit can successfully be
realized by virtue of the coupling of two branches formed as
symmetric signal paths and the adjustment of the phases in the
resonators associated with the same side, for example. The phases
of the acoustic waves to be excited in different paths can be
adjusted by, for instance, an appropriate interconnection, to be
described in detail below, of the resonators arranged in the
different signal paths.
[0011] The circuit is connected between two electrical ports with
two terminals, at least one of the ports being symmetrically
operated. A first signal path is arranged between the first
terminals of the two ports. A second signal path is arranged
between the second terminals of the two ports. At least one shunt
arm (parallel branch), arranged between the two terminals of the
first (or the second) port, can be provided.
[0012] In one variant, the first branch corresponds to the first
signal path and the second branch to the second signal path. The
first electroacoustic system is arranged in the first signal path,
and the second electroacoustic system in the second signal path. In
this case, a resonator arranged on the input side in the circuit is
referred to as the first resonator of the respective
electroacoustic system. A resonator arranged on the output side in
the circuit is referred to as the second resonator of the
respective electroacoustic system.
[0013] Different electroacoustic systems can also be arranged in
different parallel branches arranged between the first and the
second signal path. The first branch here corresponds to a shunt
arm connecting the first and second signal paths, and the second
branch corresponds to a second shunt arm connected in parallel with
the first shunt arm.
[0014] It is also possible to arrange a first electroacoustic
system in one signal path, or the first branch, and to arrange a
second electroacoustic system coupled to the latter in the parallel
branch. Preferably one electroacoustic system, coupled acoustically
and/or electrically via its coupling system to the coupling system
of an additional electroacoustic system in the parallel branch, is
arranged in each of the two signal paths (or branches).
[0015] With an appropriate interconnection of the resonators,
described below, the circuit in one advantageous variant is capable
of an impedance conversion, by a factor of 4, for example, between
the ports connected to the circuit.
[0016] In one variant, the first resonators arranged in different
branches can form a series circuit connected to the first port. The
second resonators arranged in different branches here preferably
form a parallel circuit connected to the second port.
Alternatively, the two second resonators can form a series
circuit.
[0017] In another variant, the first resonators arranged in
different branches can form a parallel circuit that is connected to
the first port. The second resonators arranged in different
branches then preferably form a series circuit that is connected to
the second port. Alternatively, the second resonators can form a
parallel circuit.
[0018] In case of more than only two branches coupled to one
another, it is possible to connect one part of the first (or
second) resonators in series and to connect the remaining first (or
second) resonators in parallel.
[0019] The first and the second coupling systems can be
galvanically, i.e., directly, coupled to one another, preferably
via a floating metal surface, with an electroacoustic signal in,
for example, the first signal path being coupled via an electrical
connection into the second signal path. The coupled signal can be
superimposed (constructively or destructively) on the signal
transmitted in the second signal path. An inductive coupling of
coupling systems via an inductor is also possible.
[0020] A capacitive coupling of the first and second coupling
systems in place of the continuous metal surface is also possible.
In principle, it is possible to combine different couplings
(capacitive, inductive, galvanic, acoustic) with one another.
Furthermore, an electromagnetic coupling of the of the coupling
system by, for instance, a transformer (e.g., electromagnetic
coupled coils, each connected to reference potential) is
possible.
[0021] In case resonators (associated with the same side of the
circuit) are coupled, an acoustic, galvanic, capacitive or
inductive coupling is possible.
[0022] Acoustic coupling can take place in the vertical direction
between resonators arranged one above the other. Acoustic coupling
can also be done laterally via lateral acoustic modes between
resonators arranged side by side.
[0023] An electrical connection between, for instance, the coupling
systems, or between the first (or second) resonators of different
electroacoustic systems, can be floating.
[0024] The floating electrical connection is preferably constituted
by a metal surface that is electrically isolated from the resonator
electrodes electroconductively connected to the ports.
[0025] The first and the second coupling system and/or, for
instance, two first resonators can also be connected electrically
to one another via an electrical connection that is connected to a
first reference potential. In one variant, the second terminal of
the first port is electrically connected to the first reference
potential.
[0026] In one variant the second resonator of the first
electroacoustic system is arranged between the first terminal of
the second port and a second reference potential. The second
resonator of the second electroacoustic system here is preferably
arranged between the second terminal of the second port and a third
reference potential.
[0027] In one advantageous variant, the first resonator, the first
coupling system and the second resonator of the first
electroacoustic system are arranged one above the other in a first
resonator stack. The first resonator, the second coupling system
and the second resonator of the second electroacoustic system here
are preferably arranged one above the other in a second resonator
stack. In one variant, the two resonator stacks are electrically
connected to one another.
[0028] In an additional advantageous variant, the first (or the
second) coupling system comprises two sub-structures electrically
connected to one another via an electrical connection that is
preferably floating with respect to the remainder of the circuit,
in particular, the terminals of the electric ports. The first
resonator of the first (or second) electroacoustic system and the
first substructure of the first (or second) coupling system are
arranged one above the other and form a first resonator stack. The
second resonator of the first (or second) electroacoustic system
and the second substructure of the first (or second) coupling
system are arranged one above the other and form a second resonator
stack.
[0029] The input-side (or output-side) resonators can be connected
in series, in inverse series, in parallel or in inverse
parallel.
[0030] The resonators are connected in series if they are connected
in series electrically and in-phase acoustically. In this case, the
electroacoustic pulse in the two resonators connected in series,
preferably arranged in different stacks, is excited in the same
direction. The resonators are connected in inverse series if they
are connected in series electrically and in out-of-phase
acoustically. In this case the electroacoustic pulses in the two
resonators connected in series, preferably arranged in different
stacks, run in opposite directions.
[0031] The resonators are connected in parallel if they are
connected in parallel electrically and in-phase acoustically. The
resonators are connected in inverse parallel if they are connected
in parallel electrically and in out-of-phase acoustically.
[0032] In case of an in-phase connection, i.e., series or parallel
connection, of two resonators, the waves in the two resonators are
excited in-phase relative to one direction. In case of an
out-of-phase connection, i.e., inverse-series or inverse-parallel
connection, of two resonators, the waves in the two resonators are
excited in out-of-phase relative to one direction.
[0033] Preferably either an in-phase connection or an out-of-phase
connection is used on both the input and the output side. In this
case, it is possible to operate the input port and the output port
symmetrically. A balun with the input or the output operated
asymmetrically is also possible. It is also possible to operate
both ports asymmetrically.
[0034] In one variant, it is also possible to use an in-phase
connection on the input side and an out-of-phase connection on the
output side. Thereby (with an electrical connection to reference
potential of the series-connected input resonators), a voltage
proportional to the differential voltage .DELTA.U=U.sub.1-U.sub.2
of input voltages U.sub.1 and U.sub.2 is formed on the output side,
the voltage U.sub.1 being applied to the first input-side terminal
and the voltage U.sub.2 being applied to the second input-side
terminal.
[0035] An impedance transformation in which the output impedance
Z.sub.out is one-fourth the input impedance Z.sub.in is achieved
with a series or inverse-series connection at the input and a
parallel or inverse-parallel connection at the output. In
particular, an impedance transformation from 200.OMEGA. to
50.OMEGA. can be achieved with this interconnection.
[0036] An impedance transformation in which the output impedance
Z.sub.out is four times the input impedance Z.sub.in is achieved
with a parallel or inverse-parallel connection at the input and a
series or inverse-series connection at the output. In particular,
an impedance transformation from 50.OMEGA. to 200.OMEGA. can be
achieved with this interconnection.
[0037] The input and the output are in principle interchangeable in
all variants. If three or more signals are used instead of two,
then other transformation ratios can be achieved by appropriate
interconnection. The transformation factor can also be fine-tuned
by adjustment of the surface areas of the input-side or output-side
resonator electrodes. For instance, the transformation factor of
the arrangement can reduced or increased by up to a factor of 2 (in
addition to the transformation ratio defined by the
interconnection) due to the larger electrode surface area for
resonators of the input side or the output side.
[0038] The invention will be described in detail below on the basis
of embodiments and the associated figures. The figures show various
embodiments of the invention on the basis of schematic
representations not drawn to scale. Identical or identically
functioning parts are labeled with the same reference symbols.
Schematically shown therein are:
[0039] FIG. 1A, the equivalent circuit diagram of a known
electroacoustic system with two resonators coupled acoustically and
electrically to one another;
[0040] FIG. 1B, the system of FIG. 1A in cross section;
[0041] FIG. 2A, the equivalent circuit diagram of a known
electroacoustic system with two resonators acoustically coupled to
one another and galvanically separated from one another;
[0042] FIG. 2B, the system of FIG. 2A in cross section;
[0043] FIG. 3, the equivalent circuit diagram of a component with
two electroacoustic systems electrically coupled to one
another;
[0044] FIG. 4A, the equivalent circuit diagram of component with
two electroacoustic systems coupled acoustically and electrically
to one another, each forming a resonator stack;
[0045] FIG. 4B, the system of FIG. 4A in cross section;
[0046] FIG. 5A, the equivalent circuit diagram of a component in
which a coupling system comprises two electrically parts arranged
in different resonator stacks;
[0047] FIG. 5B, the system of FIG. 5A in cross section;
[0048] FIGS. 5C, 5D, 5E, a plan view onto different metallization
planes of the component shown in FIG. 5B;
[0049] FIGS. 6, 7, in each case the equivalent circuit diagram of
an additional component with two acoustically and electrically
coupled systems, each forming a resonator stack;
[0050] FIG. 8, two electroacoustic systems to be coupled, with
terminals;
[0051] FIG. 9, three electroacoustic systems to be coupled, with
terminals;
[0052] FIG. 10, four electroacoustic systems to be coupled, with
terminals;
[0053] FIG. 11, resonator arrangement with input-side and
output-side in-phase interconnection and impedance
transformation;
[0054] FIGS. 12A, 12B, in each case, a resonator arrangement with
input-side and output-side in-phase series interconnection of
resonators;
[0055] FIG. 13A, resonator arrangement with input-side in-phase
interconnection, output-side out-of-phase interconnection and
impedance transformation;
[0056] FIG. 13B, resonator arrangement with input-side in-phase
series interconnection and output-side out-of-phase series
interconnection;
[0057] FIG. 14, resonator arrangement with input-side and
output-side in-phase parallel interconnection of resonators;
[0058] FIG. 15, resonator arrangement with input-side and
output-side in-phase interconnection and impedance
transformation;
[0059] FIG. 16, resonator arrangement with input-side in-phase
interconnection, output-side out-of-phase interconnection and
impedance transformation;
[0060] FIG. 17, resonator arrangement with input-side and
output-side out-of-phase series interconnection of resonators;
[0061] FIG. 18, resonator arrangement with input-side and
output-side out-of-phase interconnection and impedance
transformation;
[0062] FIG. 19, resonator arrangement with input-side out-of-phase
series interconnection and output-side in-phase series
interconnection;
[0063] FIG. 20, resonator arrangement with input-side out-of-phase
series interconnection, output-side in-phase parallel
interconnection and impedance transformation
[0064] FIG. 21A, a resonator stack operating with guided acoustic
waves, in cross section;
[0065] FIG. 21B, a plan view of an electroacoustic transducer;
[0066] FIG. 22 a component operating with GBAW, with resonator
stacks oriented side by side in the longitudinal direction, cut
away in cross section;
[0067] FIG. 23, a resonator stack operating with GBAW, with a
reference potential surface, cut away in cross section.
[0068] FIG. 1A shows an equivalent circuit diagram and FIG. 1B
shows a realization of a resonator stack--arranged on a carrier
substrate TS--with two electrically and acoustically coupled
resonators R11, R12. The resonator stack is arranged between
terminal A1 of the first port and terminal B1 of the second port.
The inner electrode is connected to a reference potential G1.
[0069] FIG. 2A shows an equivalent circuit diagram and FIG. 2B
shows a realization of an additional resonator stack with two
resonators R11, R12 acoustically coupled to one another by means of
a coupling layer K and electrically isolated from one another by
means of this layer. Resonator R11 is connected to an input port
with terminals A1, A2, and resonator R12 is connected to a
symmetric output port with terminals B1, B2. The input port is
asymmetrically connected, with terminal A2 set to a reference
potential G1.
[0070] FIG. 3 shows a circuit with two signal paths SP1 and SP2,
wherein an electroacoustic system (preferably realized by a
resonator stack) with acoustically as well as electrically coupled
resonators R11, R12, R21, R22 is arranged in each signal path SP1,
SP2. As in FIG. 1B, an electroacoustic system can comprise
resonators stacked one atop the other which share a common
electrode and are acoustically coupled to one another via a
vertical electrical coupling. First signal path SP1 is arranged
between first terminals A1, B1 of the first and second port. Second
signal path SP2 is arranged between second terminals A2, B2 of the
first and second ports. The two electroacoustic systems are
electrically connected to one another by means of a floating
electrical connection FE.
[0071] In one variant, the first port is asymmetrically connected,
second terminal A2 being conductively connected to a reference
potential G1.
[0072] Hereinafter, the first electric port is referred to as an
input port and the second electric port as the output port.
[0073] A circuit according to one variant of the invention is shown
in FIG. 4A. The circuit comprises a first branch Z1, constructed as
a signal path SP1 and a second branch Z2 constructed as a second
signal path SP2.
[0074] A first electroacoustic system that comprises two resonators
R11 and R12, acoustically coupled to one another via a first
coupling system K1 and galvanically separated from one another, is
arranged in first branch Z1. A second electroacoustic system that
comprises two resonators R21 and R22, acoustically coupled to one
another via a second coupling system K2 and galvanically separated
from one another, is arranged in second branch Z2.
[0075] The input-side resonators R11, R21 are connected here in
series with one another via a floating electrical connection FE,
and are connected to terminals A1, A2 of the first port. In one
variant, the first port is symmetrically connected. It is also
possible, however, to connect the first port asymmetrically by, for
example, conductively connecting second terminal A2 to a first
reference potential G1.
[0076] It is possible to isolate the two resonators associated with
the same side, the output-side resonators in FIG. 4A, galvanically
from one another. In this case each resonator can be operated
symmetrically. Output resonator R12 is arranged in FIG. 4A between
first terminal B1 of the output port and a second reference
potential G2. Output resonator R22 is arranged between second
terminal B2 of the output port (or of an additional output port
dependent on the first output port) and a third reference potential
G3. Reference potentials G2, G3 are preferably not identical. It is
possible, however, that G2=G3.
[0077] It is also possible, however, to operate the output port
symmetrically, in which case, as shown in FIG. 4A, the electrodes
of the output resonators connected to reference potentials G2, G3
are floating. With an asymmetrically interconnected input port,
this corresponds to a balun.
[0078] Input-side resonators R11, R12 form a first sub-circuit 1
(input circuit) and output-side resonators R12, R22 form a second
sub-circuit 2 (output circuit). Sub-circuits 1, 2 are acoustically
coupled to one another via first coupling system K1 arranged in
first signal path SP1 and second coupling system K2 arranged in
signal path SP2, and are electrically isolated from one another by
these coupling systems.
[0079] The directions of acoustic excitation in input transducers
R11, R21 are offset from another by 180.degree. in FIG. 4A.
[0080] FIG. 4B shows an example of a realization of the circuit
according to FIG. 4A as a multilayer system with two piezoelectric
layers PS1, PS2, each arranged between two metal layers ME1, ME2
and ME3, ME4, respectively, which are structured into two
electrodes of the corresponding resonator, with an acoustically
partially transmissive coupling layer K lying between metal layers
ME2 and ME3.
[0081] A resonator operating with bulk acoustic waves, resonator
R11, for example, is formed by electrodes facing one another and a
piezoelectric layer PS2 situated therebetween.
[0082] The two coupling systems K1, K2 are realized in FIG. 4B by a
common, at least partially acoustically transmissive coupling layer
K. By exciting lateral wave modes in coupling layer K, it is
possible to acoustically couple coupling systems K1, K2 in the
lateral direction. Resonators arranged side by side but in
different stacks, R11 and R12 (and/or R12 and R22), for example,
can also be acoustically coupled to one another in the lateral
direction by exciting lateral wave modes.
[0083] Input-side resonator R11, coupling system K1 and output-side
resonator R12 form a first resonator stack SCF1. Input-side
resonator R21, coupling system K2 and output-side resonator R22
form a second resonator stack SCF2. Resonators R11 and R12 (R21 and
R22, respectively) are acoustically coupled to one another in the
vertical direction via coupling system K1 (K2, respectively).
[0084] Floating electrical connection FE, preferably representing a
continuous conductive surface, is formed in metal layer ME3. The
electrical coupling of resonator stacks SCF1 and SCF2 is realized
with electrical connection FE.
[0085] First and second coupling systems K1, K2 are electrically
coupled to one another in FIGS. 4A, 5A, 6 and 7 via floating
electrical connection FE.
[0086] FIG. 5A shows the equivalent circuit diagram of one variant
of the circuit according to FIG. 4A, and FIG. 5B shows the
realization of this circuit.
[0087] The first electroacoustic system is subdivided here into two
stacks, wherein first coupling system K1 (or second coupling system
K2) comprises two parts K11 and K12 (K21 and K22, respectively).
Parts K11, K12 of first coupling system K1 and parts K21, K22 of
second coupling system K2 are respectively electrically connected
to one another via a floating electrical connection FE1, FE2. The
two floating electrical connections FE1, FE2 are arranged in the
lowermost metal layer ME1.
[0088] Resonator R11 and first part K11 of first coupling system K1
are arranged one above the other and form a first stack SCF1.
Resonator R12 and second part K12 of first coupling system K1 are
arranged one above the other and form a second stack SCF2.
Analogously, the third stack is formed from resonator R21 and first
part K21 of second coupling system K2 arranged therebelow, and the
fourth stack is formed from resonator R22 and second part K22 of
second coupling system K2 arranged therebelow.
[0089] Parts K11, K12, K21, K22 of first and second coupling
systems K1 and K2, respectively, comprise a piezoelectric layer
and, together with the electrodes surrounding this layer, each
forms a coupling resonator. The coupling resonators are
electrically connected to one another.
[0090] FIG. 5C shows the plan view of metal layer ME3 of the stack
arrangement according to FIG. 5B. The plan views of metal layers
ME2 and ME1 of the stack arrangement according to FIG. 5B are shown
in FIGS. 5D and 5E.
[0091] In FIGS. 4B and 5B, an acoustic mirror with alternately
arranged layers with low and high acoustic impedance can be
provided between carrier substrate TS and lowermost metal layer ME1
of resonator stack SCF.sub.j(j=1-4)
[0092] The series connection of input resonators R11 and R21 is
realized in FIG. 5B via an electrical connection formed in metal
layer ME3, wherein the electrodes of the aforementioned resonators
that lie on the inside of the stack are connected to one another.
In the series connection of the resonators, it is also possible to
connect the outer electrodes of the resonators and to connect their
inner electrodes to terminals A1, A2 of the input port.
[0093] FIG. 6 shows an additional possibility for interconnecting
two electroacoustic systems. The first and second electroacoustic
system respectively correspond, for example, to resonator stack
SCF1 and SCF2 according to FIG. 4B. In this case, in contrast to
FIG. 4A, the inner electrode, formed in metal layer ME2, of the
first resonator stack is connected to first terminal B1 of the
output port. The outer electrode (lowermost in FIG. 4B, situated in
metal layer ME1) of the first resonator stack is
electroconductively connected to an inner electrode, formed in
metal layer ME2, arranged in the second resonator stack.
[0094] The acoustic excitation directions in input transducers R11,
R21 are shifted in FIG. 6 by 180.degree. relative to one another.
The acoustic excitation directions in output transducers R12, R22,
on the other hand, are in phase. In case the electrical connection
between R11 and R21 is at signal ground G1, the difference between
terminals A1 and A2 relative to signal ground G1 is picked off at
output-side terminals B1 and B2.
[0095] The series connection of the resonators (output resonators
R12 and R22 in FIG. 6) via their electrodes in different metal
layers, which electrodes are arranged in different resonator stacks
or associated with different signal paths, serves to set a phase
relationship of, for example, 180.degree. between the signals that
are transmitted in signal paths SP1 and SP2.
[0096] In one variant of the embodiments shown in FIGS. 4A, 6 and
7, terminal A2 of the input port is set to signal ground G1, output
port B1, B2 being operated symmetrically.
[0097] A variant of the circuit in which signal paths SP1, SP2
comprise sub-paths connected in parallel to one another on the
output side is shown in FIG. 7. In one variant, terminals B11 and
B21 are connected to first terminal B1 and terminals B12 and B12
are connected to second terminal B2 of the output port.
[0098] In another variant, terminal B11 is connected to first
terminal B1 and terminal B21 to second terminal B2 of the output
port, terminals B12 and B22 preferably being electrically connected
to one another. Alternatively, terminal B12 can be connected to
first terminal B1 and terminal B22 to second terminal B2 of the
output port, terminals B11 and B21 preferably being electrically
connected to one another.
[0099] In the symmetrized input port in one variant, the electrical
connection between input resonators R11 and R21 is set to signal
ground G1. An output difference signal that is proportional to the
difference of the input signals is formed with output resonators
R12, R22 arranged in-phase and in series.
[0100] The interconnection possibilities present in FIGS. 4A, 6 and
7 can be summarized by the general arrangement according to FIG.
8.
[0101] FIG. 8 shows a first branch Z1 with a first electroacoustic
system arranged therein and a second branch Z2 with a second
electroacoustic system arranged therein. A11 and A12 are terminals
of the first system that are connected to the electrodes of
input-side resonator R11. B11 and B12 are terminals of the first
system that are connected to the electrodes of output-side
resonator R12. A21 and A22 are terminals of the second system that
are connected to the electrodes of output-side resonator R21. B21
and B22 are terminals of the second system that are connected to
the electrodes of output-side resonator R22.
[0102] Terminals Aij (i, j=1, 2) are electrically interconnected to
one another and connected to an input port. Terminals Bij (i, j=1,
2) are electrically interconnected to one another and connected to
an output port. The terminals that are electroconductively
connected to an outer electrode in the resonator stack are
preferably labeled with Aij, Bij (j=1). The terminals that are
electroconductively connected to an inner electrode in the
resonator stack are preferably labeled with Aij, Bij (j=2). There
is the possibility in principle of connecting the outer and/or
inner electrodes to the corresponding electric port.
[0103] Terminal 11 is preferably connected to first terminal A1 of
the input port and terminal B21 to second terminal B2 of the output
port.
[0104] Terminal A21 is preferably connected to second terminal A2
of the input port. Terminals A12 and A22 can be electrically
connected to one another. This electrical connection can be
floating in one variant (cf. FIG. 6). In another variant (cf. FIG.
7), this electrical connection can be connected to a first
reference potential. In this case, the input resonators R11, R21 of
the two electroacoustic systems are connected in series with one
another, the series circuit being connected to the input port
(A11=A1, A2=A2).
[0105] In one variant, terminal B11 is connected to first terminal
B1 of the output port. Terminals B12 and B22 here can be
electrically connected to one another, and optionally to an
additional reference potential. In this case, output resonators
R12, R22 of the two electroacoustic systems are connected to one
another in series, the series circuit being connected to the output
port (B11=B1, B12=B2).
[0106] It is also possible to connect terminal B12 to a second
reference potential, and terminal B22 to a third reference
potential (cf. FIG. 4A).
[0107] It is also possible to connect terminals A11 and A12 to one
another as well as to first terminal A1 of the input port, on the
one hand, and to connect terminals A12 and A22 to one another as
well as to second terminal A2 of the input port on the other (A11,
A21=A1; A12, A22=A2). In this case, input resonators R11, R21 of
the electroacoustic systems are interconnected in parallel, the
parallel series being connected to the input port (A1, A2).
[0108] In one variant, terminals B11 and B12 are connected to one
another as well as to first terminal B1 of the output port, on the
one hand, and terminals B12 and B22 are connected to one another as
well as to second terminal B2 of the output port on the other (B11,
B21=B1; B12, B22=B2). In this case, output resonators R12, R22 of
the electroacoustic systems are interconnected in parallel, the
parallel circuit being connected to the output port (B1, B2).
[0109] In one variant, the input port can be operated as an output
port, and the output port as an input port.
[0110] With an impedance transformation by a factor of 4 or 1/4,
respectively, two input resonators R11, R21 are connected to one
another in series and two output resonators R12, R22 are connected
to one another in parallel, or vice versa.
[0111] FIG. 9 shows three branches Z1, Z2, Z3, each with one
electroacoustic system. Third branch Z3 comprises terminals A31,
A32, B31, B32 and two resonators R31, R32 galvanically decoupled
from one another by third coupling system K3.
[0112] Two input resonators or all input resonators Rj1 (j=1, 2, 3)
can be connected in parallel or in series and be arranged between
the terminals of the input port. Two output resonators or all
output resonators Rj2 (j=1, 2, 3) can be connected in parallel or
in series and be arranged between the terminals of the output port.
To achieve an impedance transformation, it is advantageous in FIGS.
9 and 10 to connect all input resonators in series or in inverse
series, and all output resonators in parallel or in inverse
parallel.
[0113] With three or more branches, the combination of a series and
a parallel circuit of the resonators associated with the same side
can be used, in particular, to achieve impedance transformation by
an odd-numbered factor.
[0114] In the series connection of all input resonators, for
example, terminal A11 is connected to first terminal A1 of the
input port, and terminal A31 to second terminal A2 of the input
port. In one variant, terminal A12 is connected to terminal A22,
and terminal A21 to terminal A32. It is also possible, however, to
connect two input resonators, e.g., resonators R11 and R21 in
series to one another (A11=A1, A21=A2), with the third input
resonator (resonator 31) either being connected in parallel to one
of resonators R11, R21 (e.g. A31=A21. A32=A22), or in parallel to
the series circuit of resonators R11 and R21 (A31=A1, A32=A2).
[0115] At least two, in one variant all, output resonators can
likewise be arbitrarily interconnected to one another. The
description of the interconnection of input resonators also applies
to output resonators.
[0116] Four branches Z1-Z4, each with one electroacoustic system,
are shown in FIG. 10. Fourth branch Z4 comprises terminals A41,
A42, B41, B42, and two resonators R41, R42 galvanically decoupled
from one another by fourth coupling system K4.
[0117] It is possible to connect all input resonators Rj1 and/or
output resonators Rj2 to one another in series. It is also possible
to connect all input resonators Rj1 and/or output resonators Rj2 to
one another in parallel.
[0118] It is also possible to connect two resonators, input
resonators, for example (e.g., R11 and R21 on the one hand, and R31
and R41 on the other) in series and to connect the series circuits
in parallel to one another. In principle, arbitrary combinations of
series and parallel connections, the input resonators always being
galvanically decoupled from the output resonators by acoustic
coupling systems Kj (j=1-4).
[0119] Thus far the electrical interconnection of branches designed
as signal paths in FIGS. 8-10 was discussed. It is also possible,
however, to arrange the electroacoustic systems in shunt arms and
to connect the resonators, resonators Rj1 on the one hand, and
resonators Rj2 on the other, to one another electrically as
described.
[0120] A circuit according to the invention can also comprise more
than four electroacoustically coupled branches. It is possible to
couple the electroacoustic systems arranged in the different
branches to one another acoustically by, for example, coupling
systems Kj. It is also possible to couple the resonators present in
the different electroacoustic systems acoustically to one another
via an additional acoustic coupling. This can be a lateral acoustic
coupling of two resonators arranged side by side and also in
different resonator stacks.
[0121] Different variants for the interconnection of coupled
resonators are presented in FIGS. 11-20. The respective input
resonator here is acoustically coupled to the output resonator
preferably arranged in the same stack; see FIG. 8.
[0122] The input (or output) is preferably symmetrized in all
embodiments with a symmetrically operated input port (or output
port), i.e., the electrical connection of series-connected input
resonators R11, R21 (or output resonators R12, R22) is set to
signal ground. For the asymmetrically operated input port (or
output port), second terminal A2, B2 of the corresponding port is
set to signal ground (G1, G2 respectively). In a preferred variant,
the input side is related to first signal ground G1 and the output
side to second signal ground G2. Second signal ground G2 is
preferably isolated from first signal ground G1. It is also
possible for the first and second signal grounds to be connected to
one another (G2=G1). The optional connection to signal ground is
shown in FIGS. 11-20 by directed arrows.
[0123] It is possible to operate both ports symmetrically. It is
also possible to operate both ports asymmetrically. By means of two
interconnected resonator stacks, it is alternatively possible to
realize a balun, wherein one of the ports is operated symmetrically
and the other asymmetrically. By means of interconnected resonator
stacks it is further possible to realize an impedance transformer
and/or a voltage difference forming circuit. It is additionally
possible to perform a division of one signal into two separate
signals (signal splitter).
[0124] The inverse interconnection of input resonators, wherein the
electrical excitation in these resonators is shifted by 180.degree.
in comparison with the embodiments shown in the figures, is
possible in all variants. This also applies to output resonators.
The inversion can be performed on one side, either the input side
or the output side. Inverse interconnection can also be done on
both sides FIGS. 11-13B each show a resonator arrangement in which
input resonators R11, R21 are connected in series, i.e., in-phase,
one after the other.
[0125] Output resonators R12, R22 in FIG. 11 are connected to one
another in parallel and in phase, the output impedance Z.sub.out
amounting to one-fourth the input impedance Z.sub.in. Additional
resonator arrangements that realize an impedance transformation are
presented in FIGS. 13A, 13B, 15, 16, 18 and 20.
[0126] Output resonators R12, R22 can also be connected in series,
as in FIGS. 12A or 12B, wherein Z.sub.out=Z.sub.in. In FIG. 12B,
the output side is inversely connected, with the electrical
excitation running in opposite directions in resonators R11 and R12
(and R21 and R22 respectively) arranged in the respective signal
path.
[0127] Output resonators R12, R22 are connected in inverse parallel
in FIG. 13A, and in inverse series in FIG. 13B. In FIG. 13B the
same potential is present at terminals B1 and B2 if the electrical
connection between output resonators R12 and R22 is at ground
potential G2. Thus an input signal can be subdivided onto two
outputs with the same polarity. Each of FIGS. 14-16 shows a
resonator arrangement in which the input resonators R11, R21 are
connected in parallel and in-phase.
[0128] In FIG. 14, output resonators R12, R22 are connected
in-phase and in parallel. In FIG. 15, output resonators R12, R22
are connected in-phase and in series, and in inverse series in FIG.
16, with Z.sub.out.apprxeq.4Z.sub.in.
[0129] FIGS. 17-20 each show a resonator arrangement in which the
input resonators are connected in series and in out-of-phase. In
FIG. 17, the output resonators are also connected in series and in
out-of-phase. In FIG. 18, the output resonators are connected in
inverse parallel. In FIG. 19, the output resonators are connected
in series and in-phase. Identical, preferably in-phase signals
relative to signal ground G2 can be present at both output-side
terminals B1 and B2, with the splitting of the signal applied to
input side terminals A1 and A2 taking place on the output side.
Terminal B1 related to signal ground G1 defines a first output
port, and terminal B2 related to signal ground G2 a second output
port. The electrical connection between output-side resonators R12,
R22 is then at signal ground G2. In FIG. 20, the output resonators
are connected in-phase and in parallel.
[0130] In one variant of the invention it is provided that the
reference numerals A1, A2, B1, B2 each refers to one terminal of a
port related to its own signal ground. Terminals A1 and A2 in this
case are associated with two different input ports and terminals B1
and B2 with two different output ports.
[0131] In one variant, terminal A1 in FIG. 17 is associated with
the first input port related to the first signal ground, and
terminal A2 is associated with in input port related to the second
signal ground. The electrical connection between the
series-connected input resonators is related to a third signal
ground. The electrical connection between the series-connected
output resonators is floating. In this case a voltage at the output
is formed that is proportional to the difference in voltage between
the two input ports.
[0132] The circuit according to the invention can also operate with
guided bulk acoustic waves (GBAW=Guided Bulk Acoustic Waves), which
propagate in the lateral direction in a piezoelectric layer.
[0133] The realization of a circuit operating with GBAW is shown in
FIG. 21A. A resonator corresponding to resonator R11 in FIGS. 4A,
4B, 5A, 5B, 6 and 7 is formed by a transducer W11 formed in metal
layer ME2, and the underlying piezoelectric layer PS1. A
transducer, shown for the sake of example in FIG. 21B comprises
interdigitated comb-like electrodes A and B. The wave propagation
direction (the x axis in FIGS. 11A-13) is referred to as the
longitudinal direction, and the lateral direction perpendicular to
it as the transversal direction
[0134] A resonator corresponding to resonator R12 is formed by
transducer W12 formed in a metal layer ME1, and the overlying
piezoelectric layer PS1. Together, transducer W12, piezoelectric
layer PS1 and transducer W11 form a first resonator stack SCF1.
[0135] A variant in which two resonator stacks SCF1 and SCF2 are
arranged side by side in the lateral direction is shown in FIG. 22.
It s also possible to arrange the resonator stacks side by side in
the transversal direction.
[0136] The resonator corresponding to resonator R21 is formed here
by a transducer W21 and the overlying piezoelectric layer PS1. The
resonator corresponding to resonator R22 is formed by a transducer
W22 and the underlying piezoelectric layer PS1. Transducer W21,
piezoelectric layer PS1 and transducer W22 together form second
resonator stack SCF2.
[0137] The resonators associated with the first branch, comprising,
respectively, transducers W11 and W12 (as well as the resonators
associated with the second branch, comprising, respectively,
transducers W21 and W22) are acoustically coupled to one another in
the vertical direction via piezoelectric layer PS1. The direction
of acoustic coupling is indicated, as in FIGS. 11A, 12 and 13, by
arrows.
[0138] The part of piezoelectric layer PS1 arranged between
transducers W11 and W12 serves as first coupling system K1. The
part of piezoelectric layer PS1 arranged between transducers W21
and W22 serves as second coupling system K2.
[0139] Coupling systems K1 and K2 of two resonator stacks SCF1,
SCF2 arranged side by side in the longitudinal direction as in FIG.
22 can be acoustically coupled to one another by a longitudinal
acoustic wave mode. For resonator stacks SCF1, SCF2 arranged side
by side in the transversal direction, coupling systems K1 and K2
can be coupled acoustically to one another in the transversal
direction by a transversal acoustic wave mode.
[0140] An additional resonator stack operating with GBAW is shown
in cross section in FIG. 23. Differently from FIG. 21A, two
piezoelectric layers PS1 and PS2 between structured metal layers
ME1 and ME2 are provided instead of only one piezoelectric layer.
Piezoelectric layers PS1 and PS2 are separated from one another by
a third metal layer M3, in which a continuous surface at signal
ground is formed. Piezoelectric layers PS1, PS2 and the signal
ground surface between them together form a coupling system.
[0141] The surface formed between transducers W11 and W12 can be
electrically connected to a signal ground G1, but need not be.
[0142] The invention has been presented on the basis only a few
embodiments, but is not limited thereto. The input-side (or
output-side) resonators arranged in different resonator stacks can
be acoustically coupled to one another by an acoustic mode that
propagates transversely to the excitation direction (vertical
direction in the case of bulk waves). The input-side (or
output-side) resonators arranged in the same resonator stack can be
electrically coupled to one another by a common electrode.
[0143] The interconnected input resonators can be acoustically
coupled to one another by, for instance, lateral acoustic modes.
This also applies to the output resonators. In GBAW configurations,
the transducers of the resonators that are to be acoustically
coupled to one another can be formed in one metallization plane,
with the resonators acoustically coupled to one another in the
lateral direction (instead of vertical acoustic coupling). It is
advantageous in this case if the coupling system is constituted by
a combination of the piezoelectric layer and an underlying
continuous metal reference potential surface, the reference
potential surface being arranged underneath the two transducers. A
floating electrical connection can be used for the electrical
coupling of resonators or resonator groups on the input side (or
the output side).
[0144] Arbitrary combinations of input-side and output-side series
and/or parallel circuits are possible (refers to in-phase and
out-of-phase circuits).
[0145] By adjusting its thickness, the coupling system can be used
for setting a given phase shift between the coupled resonators,
which can serve, for instance, for suppressing harmonics.
[0146] An even number of resonators can be used for each side. An
odd number of resonators can also be used for each side.
[0147] With three or more branches, the combination of a series and
a parallel circuit of resonators associated with the same side can
be used.
[0148] In FIGS. 8-10, the input-side and output-side resonators can
be connected to a respective input or output port of their own. The
resonators can be interconnected such that the number of input
ports is not equal to the number of output ports. In principle, a
resonator can be connected between the terminals of two different
ports.
LIST OF REFERENCE SYMBOLS
[0149] 1 First sub-circuit (input circuit)
[0150] 2 Second sub-circuit (output circuit)
[0151] FE, FE' Floating electrical connection
[0152] R11 First resonator
[0153] R12 Second resonator
[0154] R21, Third resonator
[0155] R22 Fourth resonator
[0156] K Coupling layer
[0157] K1 First coupling system
[0158] K2 Second coupling system
[0159] K11, K12 Sub-structure of first coupling system K1
[0160] K21, K22 Sub-structure of second coupling system K2
[0161] K3, K4 Coupling systems
[0162] A1, A2 Terminals of first port
[0163] B1, B2 Terminals of the second port
[0164] Aj1 First terminal of the jth branch, j=1-4
[0165] Aj2 Second terminal of the jet branch, j=1-4
[0166] Bj1 First terminal of the jth branch, j=1-4
[0167] Bj2 Second terminal of the jth branch, j=1-4
[0168] Gj jth reference potential, j=1-3
[0169] MEj jth metal layer, j=1-3
[0170] SP1 First signal path
[0171] SP2 Second signal path
[0172] SCFj jth resonator stack, j=1-4
[0173] Z1 First branch
[0174] Z2 Second branch
* * * * *